> ## Documentation Index
> Fetch the complete documentation index at: https://docs.comfycontrol.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Subscribe to Workflow Updates

> Subscribe to real-time workflow execution updates via Server-Sent Events

## Overview

Subscribe to real-time updates for a workflow execution using Server-Sent Events (SSE). This provides live progress updates, status changes, and output information as the workflow executes.

<Info>
  This endpoint uses Server-Sent Events (SSE) for real-time updates. The connection remains open until the workflow reaches a terminal state or the maximum update limit is reached.
</Info>

## Path Parameters

<ParamField path="id" type="string" required>
  The unique identifier (UUID) of the workflow to monitor.
</ParamField>

## Response

This endpoint streams events in Server-Sent Events format. Each event contains a JSON payload with workflow status information.

### Event Data Format

<ResponseField name="status" type="string">
  Current status of the workflow.

  Possible values: `accepted`, `uploaded`, `queued`, `running`, `completed`, `cancelled`, `invalid`, `failed`
</ResponseField>

<ResponseField name="prompt" type="object">
  ComfyUI prompt information (structure varies based on workflow).
</ResponseField>

<ResponseField name="queue_number" type="integer">
  Current position in the execution queue (null if not queued).
</ResponseField>

<ResponseField name="outputs" type="array">
  Array of output media objects (populated when status is `completed`).
</ResponseField>

<ResponseField name="outputs[].id" type="string">
  Output file identifier.
</ResponseField>

<ResponseField name="outputs[].workflow_id" type="string">
  Workflow UUID.
</ResponseField>

<ResponseField name="outputs[].src" type="string">
  Signed URL to the output file.
</ResponseField>

<ResponseField name="cause" type="object">
  Error information (only present if status is `failed`).
</ResponseField>

<ResponseField name="cause.node_type" type="string">
  The ComfyUI node that caused the failure.
</ResponseField>

<ResponseField name="cause.exception_type" type="string">
  Type of exception.
</ResponseField>

<ResponseField name="cause.exception_message" type="string">
  Detailed error message.
</ResponseField>

<ResponseField name="started_at" type="string">
  ISO 8601 timestamp when execution started.
</ResponseField>

<ResponseField name="completed_at" type="string">
  ISO 8601 timestamp when execution completed.
</ResponseField>

## Example Event Stream

```
data: {"status":"queued","prompt":null,"queue_number":3,"outputs":[],"cause":null,"started_at":null,"completed_at":null}

data: {"status":"running","prompt":{"prompt_id":"abc123"},"queue_number":1,"outputs":[],"cause":null,"started_at":"2024-01-15T14:30:05Z","completed_at":null}

data: {"status":"completed","prompt":{"prompt_id":"abc123"},"queue_number":null,"outputs":[{"id":"output-1","workflow_id":"a1b2c3d4-e5f6-7890-abcd-ef1234567890","src":"https://storage.comfycontrol.app/outputs/..."}],"cause":null,"started_at":"2024-01-15T14:30:05Z","completed_at":"2024-01-15T14:32:15Z"}
```

## Connection Behavior

* **Update Interval:** \~2 seconds between updates
* **Maximum Updates:** 120 updates (\~4 minutes)
* **Auto-Close:** Connection automatically closes when workflow reaches a terminal state (`completed`, `failed`, `cancelled`)
* **Reconnection:** Client should reconnect if connection drops unexpectedly

## Error Responses

<ResponseField name="401" type="error">
  Unauthorized - invalid or missing authentication token.
</ResponseField>

<ResponseField name="404" type="error">
  Not Found - workflow with the specified ID does not exist or does not belong to your account.
</ResponseField>

## Notes

* Use this endpoint instead of polling for real-time updates
* Connection closes automatically when workflow completes
* Maximum connection time is \~4 minutes (120 updates × 2 seconds)
* For long-running workflows, reconnect if max updates is reached
* Outputs are included in the final event when status becomes `completed`
* SSE is supported by most modern HTTP clients and browsers
* Connection may be closed by network timeouts or proxies - implement reconnection logic
* Each event is a complete status snapshot, not a delta

## Example Client Code

```python theme={null}
import requests
import json

def monitor_workflow(workflow_id, token):
    url = f"https://api.comfycontrol.app/v1/workflow/{workflow_id}/subscribe"
    headers = {"Authorization": f"Bearer {token}"}
    
    with requests.get(url, headers=headers, stream=True) as response:
        for line in response.iter_lines():
            if line and line.startswith(b'data: '):
                data = json.loads(line[6:])
                print(f"Status: {data['status']}")
                
                if data['status'] in ['completed', 'failed', 'cancelled']:
                    print("Workflow finished")
                    break
```